This invention relates to siloxane-modified epoxy resin compositions with improved resistance to degradation by moisture and boiling water.
As described in U.S. Pat. No. 3,154,597, siloxane-modified epoxy resins which have both the excellent chemical resistance of epoxy resins and the excellent heat resistance of siloxane resins are known. One drawback of the siloxane-modified epoxy resins is the poor resistance of the cured compositions to degradation by boiling water and moisture. For example, when siloxane-modified epoxy resins are cured using conventional curing agents for epoxy resins, especially polyhydric carboxylic acids or their anhydrides, the electrical resistance of the composition decreases significantly when the composition is treated with boiling water.
One of the purposes of the present invention then is to improve the resistance to degradation by water of electrical properties of cured siloxane-modified epoxy resin compositions.
A companion application, Ser. No. 126,231, allowed, by the same inventor with the same filing date and assigned to the same assignee describes siloxane-modified epoxy resin compositions with improved resistance to degradation by boiling water and moisture of both adhesion to inorganic substrates and electrical resistance. In addition to the siloxane-modified epoxy resin and curing agent, the compositions contain an epoxy, methacryl, or amino organofunctional alkoxysilicon compound.